The Foundations of Chemistry

Solution

The specific heats obtained from Appendix E are as follows:

Sp. Ht.

Substance 

g

J

°C



H 2 O(
) 4.18

Hg(
) 0.138

C 6 H 6 (
) 1.74

Al(s) 0.900

Ranked from highest to lowest specific heats: H 2 O(
) C 6 H 6 (
) Al(s) Hg(
). Adding the

same amount of heat to the same size sample of these substances changes the temperature of

H 2 O(
) the least and that of Hg(
) the most. The ranking from lowest to highest final tem-

perature is

H 2 O(
) C 6 H 6 (
) Al(s) Hg(
)

You should now work Exercise 70.

40 CHAPTER 1: The Foundations of Chemistry

Key Terms

Accuracy How closely a measured value agrees with the correct
value.
Calorie Defined as exactly 4.184 joules. Originally defined as the
amount of heat required to raise the temperature of one gram
of water from 14.5°C to 15.5°C.
Chemical change A change in which one or more new sub-
stances are formed.
Chemical property See Properties.
Compound A substance composed of two or more elements in
fixed proportions. Compounds can be decomposed into their
constituent elements.
Density Mass per unit volume, D
m/V.
Element A substance that cannot be decomposed into simpler
substances by chemical means.
Endothermic Describes processes that absorb heat energy.
Energy The capacity to do work or transfer heat.
Exothermic Describes processes that release heat energy.
Extensive property A property that depends on the amount of
material in a sample.
Heat A form of energy that flows between two samples of
matter because of their difference in temperature.
Heat capacity The amount of heat required to raise the
temperature of a body (of whatever mass) one degree Celsius.
Heterogeneous mixture A mixture that does not have uniform
composition and properties throughout.
Homogeneous mixture A mixture that has uniform composi-
tion and properties throughout.

Intensive property A property that is independent of the

amount of material in a sample.

Joule A unit of energy in the SI system. One joule is 1 kgm^2 /s^2 ,

which is also 0.2390 cal.

Kinetic energy Energy that matter possesses by virtue of its mo-

tion.

Law of Conservation of Energy Energy cannot be created or

destroyed in a chemical reaction or in a physical change; it may

be changed from one form to another.

Law of Conservation of Matter No detectable change occurs

in the total quantity of matter during a chemical reaction or

during a physical change.

Law of Conservation of Matter and Energy The combined

amount of matter and energy available in the universe is fixed.

Law of Constant Composition See Law of Definite Proportions.

Law of Definite Proportions Different samples of any pure

compound contain the same elements in the same proportions

by mass; also known as the Law of Constant Composition.

Mass A measure of the amount of matter in an object. Mass is

usually measured in grams or kilograms.

Matter Anything that has mass and occupies space.

Mixture A sample of matter composed of variable amounts of

two or more substances, each of which retains its identity and

properties.

Physical change A change in which a substance changes from

one physical state to another, but no substances with different

compositions are formed.